A control rod drive mechanism for a small modular pressurized water reactor

Abstract

The present invention discloses a control rod drive mechanism for a small modular pressurized water reactor, which belongs to the field of nuclear technology and includes a protective shell with a radial dimension not exceeding 70 mm; a control rod drive body is installed inside the protective shell, and the control rod drive body includes a flange located at the left end of the protective shell for connecting with a reactor cover plate, a precision drive mechanism is arranged on the right side of the flange, a gear box is arranged on the right side of the precision drive mechanism, a position sensor unit is arranged on the right side of the gear box, and a sealed electrical input terminal is arranged on the right side of the position sensor unit. The present invention adopts the control rod drive mechanism of the small modular pressurized water reactor mentioned above, which has a compact size, a stroke of more than 1.5 meters, and an increment of less than 5 mm each time, ensuring precise control of the operation of the reactor core, and can stably operate under high temperature, high pressure, ionizing radiation and corrosive conditions.

Description

Technical Field

[0001] The invention relates to the field of nuclear technology, and in particular to a control rod driving mechanism for a small modular pressurized water reactor. Background Art

[0002] In the prior art, there are many types of control rod drive devices for nuclear reactors. In pressurized water reactors, the most common is a device with multiple electromagnetic latches, which alternately push or clamp a movable part equipped with teeth and connected to the control rod. This design is relatively simple, but it is impossible to achieve a sufficiently small step length, which is necessary to adjust the reactivity of the compact core. Current designs also use drive mechanisms based on linear stepper motors, but the drive mechanisms based on such motors are relatively inefficient and consume a lot of power. There is also a mechanical device that uses a ball screw drive, and the control rod has a precise moving step length. However, the screw of this mechanism is difficult to manufacture, and requires high precision and surface hardness. Screws with a length of more than 1 meter are technically difficult to manufacture, requiring complex processes and high costs. Summary of the invention

[0003] The object of the present invention is to provide a control rod drive mechanism for a small modular pressurized water reactor, wherein the rod stroke exceeds 1.5 meters and the increment of each movement is less than 5 mm, thereby ensuring precise control of the operation of the reactor core and capable of stable operation under high temperature, high pressure, ionizing radiation and corrosive conditions, and the mechanism has compact dimensions.

[0004] To achieve the above-mentioned purpose, the present invention provides a control rod drive mechanism for a small modular pressurized water reactor, comprising a protective shell with a radial dimension not exceeding 70 mm; a control rod drive body is installed inside the protective shell, and the control rod drive body includes a flange located at the left end of the protective shell for connecting with a reactor cover plate, a precision drive mechanism is arranged on the right side of the flange, a gear box is installed on the right side of the precision drive mechanism, a position sensor unit is installed on the right side of the gear box, and a sealed electrical input terminal is arranged on the right side of the position sensor unit.

[0005] Preferably, a shell cooling system having the same height as the shell body is provided on the outer side of the protective shell, and fins for increasing the heat exchange area are installed on the inner side of the protective shell.

[0006] Preferably, the control rod driving body is a hollow structure, with a hollow hole in the middle for the rack to move back and forth.

[0007] Preferably, the precision drive mechanism is connected to the flange by threads, and includes a rotary stepper motor, which is composed of an external stator, a rotor and an internal stator; the external stator structure is a sealed shell, the outer surface of which is wound with an electromagnetic coil, and the inner surface is provided with toothed magnetic poles; the internal stator is a fixed magnetic core made of magnetic material, has teeth and is coaxially placed with the external stator; the rotor is located in a hollow shell between the external stator and the internal stator, and the bearing used by the rotor is an anti-friction bearing.

[0008] Preferably, the electromagnetic coil is made of heat-resistant copper wire insulated by enameled wire and is filled with heat-resistant thermal conductive silicone.

[0009] Preferably, the rotary stepper motor is separately provided with a motor cooling system, which includes a heat dissipation housing equipped with a rectangular cross-section heat sink, a coolant supply port joint and a coolant outlet joint, and a step transition is adopted at the connection between the heat dissipation housing and the rotary stepper motor.

[0010] Preferably, the rack is placed coaxially with the rotor, the rack passes through a hole on the internal stator, the direction of the rack is controlled by at least two guide rollers, and the right end of the rack is hinged to a magnetic core made of magnetically permeable material to ensure stable operation of the position sensor unit.

[0011] Preferably, the gear box is connected to the precision drive mechanism via threads, and a bevel gear and a cylindrical stage are arranged in the gear box, and the bevel gear and the cylindrical stage are eccentrically arranged relative to the central axis of the gear box.

[0012] Preferably, the position sensor unit consists of a sensor housing and an inductor coil located on the sensor housing.

[0013] Therefore, the present invention adopts the above-mentioned control rod drive mechanism of a small modular pressurized water reactor, with a rod stroke of more than 1.5 meters and an increment of less than 5 mm each time, ensuring precise control of the operation of the reactor core. At the same time, it can operate stably under high temperature, high pressure, ionizing radiation and corrosive conditions, and the mechanism size is compact.

[0014] The technical solution of the present invention is further described in detail below through the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 It is a schematic diagram of the assembly structure of a control rod drive body of an embodiment of a control rod drive mechanism for a small modular pressurized water reactor of the present invention;

[0016] Figure 2 It is a schematic diagram of a precision drive mechanism and a transmission device of an embodiment of a control rod drive mechanism of a small modular pressurized water reactor of the present invention;

[0017] Figure 3 The present invention is a schematic axial cross-sectional view of a motor cooling system of a control rod drive mechanism embodiment of a small modular pressurized water reactor.

[0018] Reference numerals

[0019] 1. Rotary stepper motor; 2. Rack; 3. Gearbox; 4. Position sensor unit; 5. External stator; 6. Rotor; 7. Internal stator; 8. Electromagnetic coil; 9. Toothed magnetic poles; 10. Internal stator teeth; 11. Anti-friction bearing; 12. Motor cooling system; 13. Bevel gear; 14. Cylindrical stage; 15. Rack gear; 16. Guide roller; 17. Sensor housing; 18. Lens; 19. Fiber optic connector; 20. Receiving channel; 21. Aspheric lens. DETAILED DESCRIPTION

[0020] The technical solution of the present invention is further described below through the accompanying drawings and embodiments.

[0021] Unless otherwise defined, the technical terms or scientific terms used in the present invention should be understood by people with ordinary skills in the field to which the present invention belongs. The words "first", "second" and similar words used in the present invention do not indicate any order, quantity or importance, but are only used to distinguish different components. "Include" or "comprise" and similar words mean that the elements or objects appearing before the word include the elements or objects listed after the word and their equivalents, without excluding other elements or objects. "Connect" or "connected" and similar words are not limited to physical or mechanical connections, but may include electrical connections, whether direct or indirect. "Up", "down", "left", "right" and the like are only used to indicate relative positional relationships. When the absolute position of the described object changes, the relative positional relationship may also change accordingly.

[0022] Embodiment 1

[0023] The present invention provides a control rod drive mechanism for a small modular pressurized water reactor, comprising a protective shell with a radial dimension not exceeding 70 mm, a shell cooling system with the same height as the shell being arranged on the outside of the protective shell, and fins for increasing the heat exchange area being arranged on the inside of the protective shell.

[0024] The control rod drive body is installed inside the protective shell, such as Figure 1 The figure shows the assembly structure of the control rod drive body. The control rod drive body is a hollow structure with a hollow hole in the middle for two teeth to move back and forth. A flange for connecting to the reactor cover is installed on the left end of the control rod drive body, and a precision drive mechanism is connected to the right side of the flange through threads. Figure 2The figure shows a schematic diagram of a precision drive mechanism and a transmission device. The precision drive mechanism includes a rotary stepper motor 1. The rotary stepper motor 1 is a synchronous four-phase DC motor, which is composed of an external stator 5, a rotor 6 and an internal stator 7. The rotor is driven to rotate by electromagnetic force. The external stator 5 is a sealed shell. An electromagnetic coil 8 is wound around the outer surface of the sealed shell. The electromagnetic coil 8 is made of heat-resistant copper wire insulated by enameled wire and filled with heat-resistant thermal conductive silica gel for heat conduction. The inner surface of the sealed shell has toothed magnetic poles 9; the internal stator 7 is a fixed magnetic core made of magnetic material, with internal stator teeth 10, and is coaxially placed with the external stator 5. The internal stator 7 can increase the working gap area of ​​the motor and increase the torque without significantly increasing the energy consumption; the rotor 6 is a hollow shell located between the external stator 5 and the internal stator 7, and the bearing used is an anti-friction bearing 11.

[0025] The rotary stepper motor 1 is separately provided with a motor cooling system 12 to ensure reliable operation of the device in a high temperature environment. The axial section of the motor cooling system 12 is shown as follows: Figure 3 As shown, it includes a heat dissipation housing with a rectangular cross-section heat sink, a coolant supply port joint and a coolant outlet joint. The connection between the heat dissipation housing and the rotary stepping motor 1 adopts a stepped transition. A gear box 3 is installed on the right side of the precision drive mechanism. The gear box 3 is connected to the precision drive mechanism through threads. A bevel gear 13 and a cylindrical stage 14 are arranged in the gear box 3 to convert the rotary motion of the motor into the linear motion of the control rod. The gear rack is compactly arranged. The bevel gear 13 and the cylindrical stage 14 are eccentrically arranged relative to the overall central axis of the device, in order to make the rack 2 coaxial with the rotor 6.

[0026] The rack 2 passes through the hole on the internal stator 7, and the direction is controlled by at least two guide rollers 16 to prevent deviation from the vertical direction. The right end of the rack 2 is hinged with a magnetic core made of magnetically permeable material to ensure the operation of the position sensor. The right side of the gearbox 3 is connected with a position sensor unit 4 through a thread. The right side of the position sensor unit 4 is provided with a sealed electrical input terminal. The position sensor unit 4 adopts an inductive discrete position sensor, which is composed of a sensor housing 17 and an inductor coil located on the sensor housing 17. The response of the position sensor is determined by the impedance difference between two adjacent coils. The accuracy of the control rod position detection is improved through differential activation.

[0027] During the assembly process of the control rod drive mechanism, the meshing quality of the rack 2 and the gear is controlled, and the response position of the position sensor unit 4 is adjusted. The components are connected by threads to ensure the strength of the joints and maintain the internal pressure, and then sealed by welding to ensure that the medium does not leak from the inner cavity of the device. When working, the control rod drive mechanism is installed on the reactor cover plate through a flange, adopts a vertical layout, compact arrangement, and ensures the uniformity of the seal by sequentially tightening the threaded connection.

[0028] The rotary stepper motor 1 transmits torque to the gearbox 3 through the rotation of the rotor 6. The gearbox 3 is used to convert the rotary motion of the rotor 6 into the linear motion of the rack 2 and the control rod rigidly connected to the rack 2, so that the stroke of the control rod exceeds 1.5 meters. The rotor 6 is not connected to the external stator 5 and the internal stator 7, and plays the role of a safety clutch and a tripping device. The gearbox 3 provides the step value required for the control rod from the perspective of reactor operation, and each movement increment is less than 5 mm, ensuring accurate control of the operation of the reactor core. The position sensor unit 4 is used to discretely control the position of the control rod within the working range and send a corresponding signal to the control device. In the normal operation mode, the control rod drive mechanism can combine the automatic adjustment mechanism and the reactivity compensation function to gradually withdraw or insert the control rod into the active area of ​​the reactor according to the signal of the control device to ensure automatic maintenance of the power level or compensation of fuel consumption. In the fast power reduction mode, the rotary stepper motor 1 inserts the control rod into the active area at the fastest speed. In the event of an emergency protection mode or power outage, the rotary stepper motor 1 is powered off and the control rods are inserted into the reactor active area under their own weight to ensure that the fission chain reaction is stopped.

[0029] Therefore, the present invention adopts the control rod drive mechanism of the above-mentioned small modular pressurized water reactor, which has compact size and each movement increment is less than 5 mm, ensuring precise control of the operation of the reactor core and stable operation under high temperature, high pressure, ionizing radiation and corrosive conditions.

[0030] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that they can still modify or replace the technical solution of the present invention with equivalents, and these modifications or equivalent replacements cannot cause the modified technical solution to deviate from the spirit and scope of the technical solution of the present invention.

Claims

1. A control rod drive mechanism for a small modular pressurized water reactor, characterized in that: It comprises a protective shell, the radial dimension of which does not exceed 70 mm; a control rod drive body is installed inside the protective shell, the control rod drive body comprises a flange located at the left end of the protective shell for connecting with the reactor cover plate, a precision drive mechanism is arranged on the right side of the flange, a gear box is arranged on the right side of the precision drive mechanism, a position sensor unit is arranged on the right side of the gear box, and a sealed electrical input terminal is arranged on the right side of the position sensor unit; The control rod driving body is a hollow structure, with a hollow hole in the middle for the rack to move back and forth; The precision drive mechanism is connected to the flange by threads, and comprises a rotary stepping motor, which is composed of an external stator, a rotor and an internal stator; the external stator structure is a sealed shell, the outer surface of which is wound with an electromagnetic coil, and the inner surface is provided with toothed magnetic poles; the internal stator is a fixed magnetic core made of magnetic material, has teeth and is coaxially placed with the external stator; the rotor is located in a hollow shell between the external stator and the internal stator, and the bearing used by the rotor is an anti-friction bearing; The rack is coaxially placed with the rotor, the rack passes through a hole on the internal stator, the direction of the rack is controlled by at least two guide rollers, and the right end of the rack is hinged to a magnetic core made of a magnetically permeable material to ensure stable operation of the position sensor unit; The gearbox is connected to the precision drive mechanism by threads, and a bevel gear and a cylindrical stage are arranged in the gearbox, and the bevel gear and the cylindrical stage are eccentrically arranged relative to the central axis of the gearbox; The position sensor unit adopts an inductive discrete position sensor, which is composed of a sensor housing and an inductive coil located on the sensor housing. The response of the position sensor is determined by the impedance difference between two adjacent coils, and the accuracy of control rod position detection is improved through differential activation.

2. The control rod drive mechanism of a small modular pressurized water reactor according to claim 1, characterized in that: The outer side of the protective shell is provided with a shell cooling system having the same height as the shell body, and the inner side of the protective shell is provided with fins for increasing the heat exchange area.

3. The control rod drive mechanism of a small modular pressurized water reactor according to claim 1, characterized in that: The electromagnetic coil is made of heat-resistant copper wire insulated by enameled wire and is filled with heat-resistant thermal conductive silica gel.

4. The control rod drive mechanism of a small modular pressurized water reactor according to claim 1, characterized in that: The rotary stepper motor is independently provided with a motor cooling system, which includes a heat dissipation housing equipped with a rectangular cross-section heat sink, a coolant supply port joint and a coolant outlet joint. The connection between the heat dissipation housing and the rotary stepper motor adopts a stepped transition.

5. The control rod drive mechanism of a small modular pressurized water reactor according to claim 1, characterized in that: The position sensor unit is composed of a sensor housing and an inductor coil located on the sensor housing.

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